Tzi'na Enclave

The Tau's expansion in the sector in recent centuries has been rapid. Fortunately for Imperial interests, their faster-than-light technology – both communicative and physical response – has remained relatively limited.

Having a centralised command base increasingly meant that the Tau struggled to respond to raids on their border worlds. The Tau's innovation was the establishment, in the dying years of the 41st Millennium, of the Enclave regions; semi-autonomous zones of the Brightsword Protectorate that are responsible in the first instance for their own defence. 

the Tzi'Na Enclave is the largest Enclave currently known to the Imperium (though it is possible that larger Enclaves exist deeper in the Brightsword region, or even in wilderness space), and is, in Tau terms at least, heavily militarised, with a powerful fleet presence and a number of standing armies on its primary worlds. The Enclave sits between the Hesiod-Siculus and Starfire subsectors, corewards of – though continuous with – Protectorate space.